In particular, when applying the techniques of loop quantum gravity (LQG) to homogeneous and isotropic universe, namely loop quantum cosmology (LQC) [1]}, it was shown that,
purely due to quantum geometric effects, the big bang singularity is generically resolved and replaced by a quantum bounce at which the spacetime curvature becomes Planckian [2]}, [3]}, [4]}, [5]}. The robustness of the singularity resolution has been shown for a variety of isotropic and anisotropic spacetimes [6]}. Interestingly, there exists a reliable effective spacetime description,
which has been used to confirm a generic resolution of all strong curvature singularities [7]}. Various phenomenological implications have been studied using this effective spacetime description,
whose validity has been verified for isotropic and anisotropic spacetimes [8]}, [9]}, [10]}, [11]}, [12]}. For low energy inflation models with a positive spatial curvature,
the singularity resolution and a successful onset of inflation for classically inadmissible initial conditions have been demonstrated [13]}, [14]}, [15]}.
